Recovery of copper-vanadium catalist



United States Patent RECVERY F CUPPER-VANADEUM CATALYST David Morgan lheyshon and .lohn Stewart, Manchester,

England, assignors to llinperia Chemicai industries Limited, London, England, a corporation of Great Britain No Drawing. liiied Dec. 18, 1961, Ser. No. 160,334 Claims priority, application Great Britain, dan. 23, i961,

2578/61 4 Claims. (Cl. 252-413) This invention Irelate-s to a process for recovering thc copper-vanadium catalyst from the waste liquors obtained in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol and/ or cyclohexanone and is a modiication of the processes described in UK. patent specilication No. 756,679. In connection with the present invention the term copper-Vanadium catalyst includes any compounds of copper and vanadium which may be formed in the various processes referred to.

According to U.K. Patent No. 572,260 in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol, cyclohexanone or of mixtures containing them obtained by the oxidation of cyclohexane, the nitric acid oxidation is carried out in the presence of both vanadium and copper, either as such or in the form of their oxides or salts, the amount of copper used being between 1 part and 40 parts by weight per part by weight ofthe vanadium used. f The waste liquors obtained in the above process after isolation of the adipic acid by filtration, contains valuable amounts of catalyst salts and by-prod- Vuct organic Vacids such as glutaric and succinic acids.

According to U.K. Patent No. 756,679 the copper-vana x dium catalyst and by-products from the abovementioned has been removed and isolating the catalyst and by-products from the residue.

According to the present invention we provide a procd' ess for recovering the copper-vanadium catalyst from the waste liquors obtained in the manufacture of adipic acid by the nitric acid oxidation of cyclohexanol and/or cyclohexanone or rnixturescontaining them which cornprises the steps of adding sulphuric or phosphoric acid to the Waste liquor in an amount slightly more than equivalent to the nitrate salts present evaporatingnitric acid and water therefrom, lteringthe molten residue to separate the insoluble catalyst, redissolving the catalyst in Water or dilute nitric acid, reprecipitating the catalsyt at a pH above 7 and washing the precipitated catalyst with water.

Evaporation of nitric acid and water by heating is preferably performed under reduced pressure. The evaporation may be performed rapidly atvtemperatures up to about 150 C. provided vigorous reaction and decomposition is prevented, by blowing steam conveniently at a temperature of from 100 C. to 170 C. into the liquors or by continuous addition thereto of fresh or partially concentrated Waste liquors, preferably at a temperature of from 40 C. to 90 C. The rate of addition of steam or fresh waste liquors is adjusted so as to prevent undue rise in temperature, or the formation of nitrous gases above about 95 C. It may also be convenient to blow air through the hot molten residue in order to remove any remaining small amount of nitric acid. Owing to the presence of added mineral acid the whole of the nitric acid, both free and Ithat originally combined as salt may be readily removed.

After the precipitated catalyst has been purified in the HCC above manner it may be redissolved in nitric acid and returned for use in the oxidation of cyclohexanol and cyclohexanone.

We have found that by the puriiication process of our invention lrecovered catalyst of excellent quality is obtained, which contains a lower proportion of organic irnpurities 'than catalyst recovered by previously known methods.

In operating the process of the invention it is found convenient to reprecipitate the catalyst at a pH above 7 and preferably between 8 and 9 by the use of'alkalis such as the alkali metal and alkaline earth metal hydroxides and carbonates, but we prefer toV use alkali metal hydroxides such as sodium hydroxide.

The invention is illustrated but not limited by the following examplein which parts and percentages are by Weight.

Example ture is held at 90-95o C. for 1 hour, the precipitated catalyst ltered oit' and washed on the iilter with four lots of 20 parts each of water. The catalyst is then substantially free from organic matter and Iis suitable when dissolved in nitric acid for direct re-use in the oxidation to adipic acid of cyclohexanol, cyclohexanone or the product of air 4 oxidised cyclohexane.

lf desired the `crude catalyst may be initially dissolved in water instead of 5% nitric acid.

What we claim is:

1. A process for the recovery of copper-vanadium catalyst from the waste iiquor obtained in the manufacture of adipic acid by nitric acid oxidation of a member of the group consisting of cyclohexanol, cyclohexanone, and mixtures thereof and containing nitrate salts as a result of said oxidation, said process comprising the steps of adding to the waste liquor an acid selected from the group consisting of sulphuric acid and phosphoric acid in an amount slightly more than the chemical equivalent of the nitrate salts present in the Waste liquor, evapora-ting substantially all of the Water and nitric acid from said Waste liquor by the application ofk heat thereto, filtering the molten residue to separate the insoluble catalyst, redissolving the catalyst in a member of the group consisting of Water and dilute nitric acid, reprecipitating the catalyst by adding alkali thereto to raise the pH to above 7 and Washing the precipitated catalyst with water.

' 2. A process according to claim 1 wherein after washing with water the precipitated catalyst is redissolved in nitric acid.

3, A process according to claim 1 wherein the reprecipitating step is conducted at a pH of from 8 to 9.

4. A process according .to claim 1 wherein the alkali is:-

an alkali selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides and alkaline earth metal carbonates.

MAURICE A. BRINDISI, Primary Examiner. 

1. A PROCESS FOR THE RECOVERY OF COPPER-VANADIUM CATALYST FROM THE WASTE LIQUOR OBTAINED IN THE MANUFACTURE OF ADIPIC ACID BY NITRIC ACID OXIDATION OF A MEMBER OF THE GROUP CONSISTING OF CYCLOHEXANOL, CYCLOHEXANONE, AND MIXTURES THEREOF AND CONTAINING NITRATE SALTS AS A RESULT OF SAID OXIDATION, SAID PROCESS COMPRISING THE STEPS OF ADDING TO THE WASTE LIQUOR AN ACID SELECTED FROM THE GROUP CONSISTING OF SULPHURIC ACID AND PHOSPHORIC ACID IN AN AMOUNT SLIGHTLY MORE THAN THE CHEMICAL EQUIVALENT OF THE NITRATE SALTS PRESENT IN THE WASTE LIQUOR, EVAPORATING SUBSTANTIALLY ALL OF THE WATER AND NITRIC ACID FROM SAID WASTE LIQUOR BY THE APPLICATION OF HEAT THERETO, FILTERING THE MOLTEN RESIDUE TO SEPERATE THE INSOLUBLE CATALYST, REDISSOLVING THE CATALYST IN A MEMBER OF THE GROUP CONSISTING OF WATER AND DILUTE NITRIC ACID, REPRECIPITATING THE CATALYST BY ADDING ALKALI THERETO TO RAISE THE PH TO ABOVE 7 AND WASHING THE PRECIPITATED CATALYST WITH WATER. 